The Grignard reagent, on reaction with acetone, forms :

Options

A. Tertiary alcohol
B. Secondary alcohol
C. Acetic acid
D. Acetaldehyde

Answer

To solve the question regarding the reaction of a Grignard reagent with acetone, we will follow these steps:

### Step-by-Step Solution:

1. **Identify the Grignard Reagent**:
A Grignard reagent is represented as R-MgX, where R is an alkyl group and X is a halogen. For example, if R is a methyl group (CH3), the Grignard reagent would be CH3-MgX.

**Hint**: Remember that Grignard reagents are organometallic compounds with a carbon-metal bond.

2. **Identify Acetone**:
Acetone is a ketone with the formula (CH3)2C=O. It has a carbonyl group (C=O) where the carbon atom is electrophilic due to the partial positive charge.

**Hint**: Recognize that the carbonyl carbon in ketones is susceptible to nucleophilic attack.

3. **Nucleophilic Attack**:
The Grignard reagent acts as a nucleophile. The R group from the Grignard reagent (R-) will attack the electrophilic carbon of the carbonyl group in acetone. This results in the formation of a tetrahedral intermediate.

**Hint**: The nucleophile (R-) will attack the carbonyl carbon, leading to a change in hybridization from sp2 to sp3.

4. **Formation of Tertiary Alcohol**:
After the nucleophilic attack, the tetrahedral intermediate can undergo hydrolysis (reaction with water). This will yield a tertiary alcohol. The general structure will be R-C(OH)(CH3)2, where R is the alkyl group from the Grignard reagent.

**Hint**: Hydrolysis involves adding water (H2O) to the intermediate, resulting in the formation of an alcohol.

5. **Final Product**:
The final product of the reaction between the Grignard reagent and acetone is a tertiary alcohol. This is because the carbon that was originally part of the carbonyl group is now bonded to three other carbon groups (two from acetone and one from the Grignard reagent).

**Hint**: Tertiary alcohols have three alkyl groups attached to the carbon bearing the hydroxyl (-OH) group.

### Conclusion:
The Grignard reagent, when reacted with acetone, forms a tertiary alcohol.

### Final Answer:
The correct answer is a tertiary alcohol.